As a method of AF, an image surface phase difference AF has been known. In a solid-state imaging device that realizes image surface phase difference AF, phase difference pixels for dividing incident light for pupils are provided in predetermined positions, as well as regular pixels for obtaining pixel signals.
FIG. 1 is a cross-sectional view of an example structure of a solid-state imaging device including a conventional phase difference pixel. In the drawing, the right side is a standard pixel 10, and the left side is a phase difference pixel 11.
In this solid-state imaging device, the standard pixel 10 and the phase difference pixel 11 each have an on-chip lens 12, a color filter 13, and a light receiving region 16, in this order from the upper layer side (the light incidence surface side).
A light shielding film 14 that has an aperture portion 15 having an aperture deviated from the optical axis of the on-chip lens 12 is also provided in the phase difference pixel 11, but is not provided in the standard pixel 10.
In the drawing, the on-chip lenses 12 of the standard pixel 10 and the phase difference pixel 11 have identical shapes, and are designed so that the focal positions are adjusted to the surfaces of the light receiving regions 16 (in other words, incident light fluxes are gathered on the surfaces of the light receiving regions 16). In this case, optimum optical properties of the standard pixel 10 can be achieved. As for the phase difference pixel 11, however, the sensitivity for incident light from oblique directions becomes lower due to the existence of the light shielding film 14, and the pupil separation performance is degraded, for example.
So as to prevent degradation of the separation performance of the phase difference pixel 11, the shape of the on-chip lens 12 should be adjusted so that the focal position is located at the height of the light shielding film 14. In that case, however, the optimum optical properties of the standard pixel 10 are of course not achieved.
In view of this, a structure that prevents degradation of the optical properties of the standard pixel 10 while maintaining the separation performance of the phase difference pixel 11 has been suggested (see Patent Document 1, for example).
FIG. 2 is a cross-sectional view of an example of such a structure. This example structure differs from the structure shown in FIG. 1 in that the focal positions of the on-chip lenses 12 are located at the height of the light shielding film 14, and optical waveguides 17 are additionally provided on the lower layer side of the light shielding film 14.